Conventionally, a non-contact voltage measuring apparatus that measures an AC voltage (measurement object voltage) flowing through a conductive wire covered with an insulation coating without touching the conductive wire.
The non-contact voltage measuring apparatus measures the measurement object voltage in a manner as described below. A detection probe is brought close to the insulation coating of the conductive wire to detect the voltage. When the insulation coating and the detection probe get in close proximity to each other, a coupling capacitance is created between the detection probe and the conductive wire. If an AC current flows through the conductive wire when a coupling capacitance is created between the detection probe and the conductive wire, an induced voltage is generated on the detection probe. The voltage value of the induced voltage and an electrostatic capacitance value of the coupling capacitance are used to calculate a measurement object voltage.
Patent Document 1 describes, as an example of a non-contact voltage measuring apparatus, a non-contact voltage detecting apparatus equipped with a detection probe covered with a flexible material. Because the detection probe is flexible, a user can improve contact between an electric wire and the detection probe and can increase a contact area between the electric wire and the detection probe by winding the detection probe around an insulation coating of the electric wire. Therefore, a coupling capacitance created between the detection probe and a core wire in the electric wire is increased, and fluctuation (variation) of the coupling capacitance between an electric wire and the detection probe is reduced. A measurement object voltage is measured accurately by using the coupling capacitance that has a large absolute value and a small fluctuation.